Usage of FilteredSelectMultiple in custom models

multiselect.py

from django.contrib.admin.widgets import FilteredSelectMultiple
from django import forms

def widget(model_reference, field, title, titlew):
    class WidgetForm(forms.ModelForm):
        vars()[field] = forms.ModelMultipleChoiceField(queryset=model_reference.objects.all(),
                                              label=(title),
                                              widget=FilteredSelectMultiple(
                                                        (titlew),
                                                        False,
                                                     ))
        class Media:
            css = {
                'all':('/media/css/widgets.css',),
            }
            # jsi18n is required by the widget
            js = ('/admin/jsi18n/',)
    
        class Meta:
            model = model_reference
            
    return WidgetForm

usage.py

from path.to.multiselect import widget
from myapp.models import MyModel

class MyAdminModel(admin.ModelAdmin):
    form = widget(MyModel, 'field_name', 'Field title', 'field_widget_title', )